Governing Equations for Weakly Ionized Plasma Flowfields of Aerospace Vehicles

Abstract

A generalized set of conservative equations for simulating the flowfield in a hypersonic weakly ionized gas flows is presented. Additional numerical and physical complexities associated with the plasma state are identified and discussed, including the influence of external and space charge fields and the nonequilibrium coupling of reactive and nonreactive collisions. A restricted set of equations is then employed to simulate and analyze the flowfield of an air plasma generated by associative ionization. With use of a seven-species air model, details of the plasma flowfields are presented and compared with available experiments. Refined estimates of dissociation products, which are the precursors to the ionization reaction, are obtained. Specific attention is given to limiting forms of the electron diffusion coefficient and the influence of vibration-dissociation coupling. Details of the chemical reactions in the flowfield influencing the elastic and inelastic collisional energy transfer are reported to highlight the more important species and reaction mechanisms.